Lithium compound containing electric cells and batteries containing such cells are modern means for energy storage devices. For example, lithium ion batteries have been major power sources for cell phones, laptop computers and a host of other portable electronic consumer products. Penetration of this technology into the transportation market and other large scale applications continues to place ever-increasing demands for higher energy density, higher power density and better cycle life.
Electrolytes for lithium compound containing energy storage devices are mixtures comprised of one or more highly soluble lithium salts and inorganic additives dissolved in one or more organic solvents. Electrolytes are responsible for ionic conduction between the cathode and the anode in the battery and thus essential to the operation of the system. The conventional carbonate-based electrolytes have been successfully applied in commercial 4V lithium ion batteries. Electrolytes having high level performance are desired when the cell operating window is extended to higher potential to avoid decomposition on the highly oxidative surface of charged cathodes. It is also desired that there be improved the interaction between electrolyte and cathode at high voltage.
The use of LiFSI in electrochemical devices is known. LiFSI based electrolytes have high conductivity, thus providing better rate and low temperature performance. However, its application in the battery is limited by its metal corrosion property because metallic material is an essential part of the battery. For example, Al is used as current collector for the positive electrode, and stainless steel may be used as the casing material. It is also known that the use of LiPF6 together with LiFSI may passivize the metal, however, the method has limited effect, especially at high working voltage. There remains a need of method through which LiFSI may be utilized for its beneficial effects in rechargeable battery while not causing, performance degradation to the battery